The correct answer is: German soldiers were not all supportive of Hitler.
The speaker uses the phrase "Hitler has been so kind as to announce to his loyal, devoted people..." ironically to emphasize the existence of some insubordinate German soldiers. The credibility in this sarcastic statement is evidenced when the speaker reveals the happening of a "cowardly attempt to take the Führer's life" by the hands of one of these soldiers.
This act effectively proves the disloyalty of some German soldiers on Hitler's intent.